As an alternative or add-on to satellite-based positioning systems, positioning systems in which a present position of a terminal is estimated based on a list of communication nodes (such as for instance cellular base stations, access points or beacons) that can presently be heard by the terminal and a database that contains identifiers and positions of the communication nodes and/or models for the coverage areas for a number of communication nodes have gained recent interest.
Given that the communication node positions are known and distances from the terminal to the communication nodes can be estimated, the terminal's position can for instance be estimated through triangulation. Distances between a terminal and the heard communication nodes can for instance be estimated based on the path loss using a channel model (i.e. how much the signal attenuates between the terminal and the communication node) or based on timing (or round-trip timing) measurements (i.e. information expressing how long signals propagate between terminal and communication node).
Alternatively or additionally, if the coverage areas of the communication nodes are known, then a terminal may pick the coverage areas for the heard communication nodes and determine its own position based on these coverage areas.